Field of the Invention
The present invention generally relates to the fields of optoacoustic-ultrasonic methods and contrast agents suitable for imaging and sensing purposes, and in particular, but not limited to, nanocomposite particles designed to have properties to maximize contrast during optoacoustic-ultrasonic imaging and sensing procedures.
Description of the Related Art
Optoacoustic imaging, sensing and monitoring are rapidly emerging biomedical technologies with significant potential for a growing number of applications in detection and treatment of cancer and vascular diseases (1). Combining optoacoustic imaging with ultrasonic imaging is technologically natural and beneficial from a biomedical prospective because the two types of imaging provide complementary information to the physician (2). The acoustic contrast of ultrasonic imaging based on density and speed of sound can provide fine morphological details, while optoacoustic imaging has better contrast for blood and can be used to acquire functional information with molecular specificity. That is why optoacoustic molecular and functional imaging combined and coregistered with ultrasonic imaging is thought to have the most merit for health care.
Exogenous contrast agents are administered to the body for purposes of biomedical imaging, sensing and monitoring therapeutic and surgical interventions in situations where a specific volume in the body of medical interest does not have sufficient endogenous contrast. While ultrasonic contrast agents based on encapsulated gas bubbles have been developed and used in clinics, necessarily nontoxic and sufficiently effective optoacoustic contrast agents have not been developed. Ultrasonic contrast agents are relatively successful because biological tissues do not possess strong echogenicity. The problem and the challenge associated with optoacoustic imaging is that optoacoustic contrast agents must effectively compete with the contrast of red blood cells and achieve sufficient contrast enhancement in concentrations substantially lower than the concentration of hemoglobin in blood.
With a large number of proposed designs for optoacoustic contrast agents (3) and recently two different designs for dual modality optoacoustic-ultrasonic contrast agents (4-6), none of them met the challenge of being necessarily nontoxic and sufficiently effective in generation of ultrasonic, i.e., pressure, waves in response to optical illumination. Contrast agents based on nanocomposite particles are more effective compared with molecular probes because the optoacoustic signals they emit or ultrasonic signals they reflect are proportional to their volume.
Thus, there is a present need for dual contrast agents with improved capabilities for contrast enhanced optoacoustic-ultrasonic imaging and sensing in vivo or in vitro. Specifically, the prior art is deficient in non-toxic, nanocomposite particles that both generate and reflect detectable ultrasonic signals upon interaction with optical and ultrasonic energy. The present invention fulfills this longstanding need and desire in the art.